Earth Isn't So Special Anymore

Relative sizes of
Kepler habitable zone planets discovered as of April 18, 2013.
Left to right: Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f,
and Earth.

Every day, with the help of NASA's Kepler telescope, astronomers get closer
and closer to finding more planets like our Earth that circle
stars like our sun.

On Thursday, researchers announced the discovery of two new
planetary systems, each which contain planets that circle a star
similar to our sun, and within a distance that would allow that
planet to support liquid water, also known as the "habitable
zone."

"With all of these discoveries we're finding, Earth is looking
less and less like a special place and more like there's
Earth-like things everywhere," said Tom Barclay, Kepler scientist
at the Bay Area Environmental Research Institute in Sonoma,
California, according to
CNN's Elizabeth Landau.

The "habitable" zone means that a planet is not too close to its
host star that liquid water would boil away, and not too far that
liquid water would freeze. It is in the perfect spot between fire
and ice, William Borucki, Kepler's principal science
investigator, said at a news conference on Thursday.

Kepler-62e and Kepler-62f are somewhat bigger than Earth (they
are known as super-Earths), but scientists say they are the best
planet candidates for habitability found yet because of their
size. Past candidates have been much bigger than Earth.

Another newly discovered two planet-system, which circles a
sun-like star called Kepler-69, includes one planet that orbits
in the habitable zone. Kepler-69c is even bigger
than Kepler-62e and Kepler-62f, however.

Scientists don't know what kind of life is on these planets or
even their exact composition — they could be rocky and Mars-like
— but it does mean that we are well on the way to finding more
planets like our own.

These planets could hold alien species, or be habitable for
colonies of humans. It's too early to tell.